Extending her political star power to other Democrats facing potentially tough re-election bids in 2014, Sen. Elizabeth Warren, D-Mass., sent a fundraising letter to supporters on Tuesday warning that without their support, the U.S. Senate could, like the House, end up under Republican control.

In a pitch for Sen. Jeanne Shaheen of New Hampshire, Sen. Mary Landrieu of Louisiana, and Sen. Kay Hagan of North Carolina, Warren said that without Democrats retaining control of the Senate, GOP priorities she described as extreme may pervade both chambers of congress following the 2014 mid-term elections.

"The Republicans in Washington have taken their vision for America to a dangerous new extreme. They've tried to repeal health care reform 42 times. They've insisted on keeping in place a sequester that takes an axe to funding for Head Start, Meals on Wheels, and unemployment benefits," Warren wrote. "And now they've threatened to shut down the government if we don't make even more cuts. To win these budget fights in the short-term, we need to fight back, together. And to win these budget fights in the long-term, we need to keep Democrats in control of the U.S. Senate."

In the most recent dispatch on the polls surrounding the mid-term elections, the blog characterizes Landrieu and Hagan's re-election bids as toss-ups with strong Republican challengers, but considers Shaheen re-election as safe, due in part to the lack of a strong declared GOP contender for the seat.

Scott Brown, a former GOP U.S. senator from Massachusetts, is considered Shaheen's strongest Republican competitor, as he's hinted at a run in the Granite State where he owns a vacation home. A Public Policy Polling survey released last week showed Shaheen winning over Brown by only four points in a hypothetical 2014 Senate campaign match-up. Brown lost his Senate seat to Warren in 2012.

Warren also made a fundraising pitch this week for Sen. Jeff Merkley, D-Oregon, offering up a chance to share lunch with her for as little as a $3 donation, according to published reports.Silver's blog characterized Merkley's seat as safe in 2014, but noted that Republicans only need to win six new Senate seats to gain control of the Senate, allowing the GOP to override a potential tie-breaking vote by Vice President Joe Biden.